cvs commit: src/sys/alpha/alpha mem.c src/sys/alpha/conf GENERIC src/sys/alpha/include memdev.h src/sys/amd64/amd64 io.c mem.c src/sys/amd64/conf GENERIC NOTES src/sys/amd64/include iodev.h memdev.h src/sys/conf NOTES files files.alpha files.amd64 ...

[Sam Leffler]

On Monday 02 August 2004 07:54 pm, Don Lewis wrote:
> On  3 Aug, Alexey Dokuchaev wrote:
> > On Mon, Aug 02, 2004 at 04:00:00PM -0400, John Baldwin wrote:
> >> Why in the world are /dev/null and /dev/zero optional?  /dev/[k]mem
> >> and /dev/io I can accept for those with uber-high security paranoia, but
> >> I can't think of any good reason to have a kernel without /dev/null and
> >> /dev/zero.  To me it seems that this creates way more foot shooting
> >> potential than benefit.  It's one thing to have device drivers for
> >> hardware that may or may not be present optional, but /dev/null and
> >> /dev/zero do not fall into that case.
> >
> > OTOH, if someone wants to build mega-tight kernel image with everything
> > possible taken out by modules, modularizing /dev/null and /dev/zero
> > might make some sence.  We already have /dev/random as a module anyways.
>
> You might have trouble doing anything useful on the system without
> /dev/null.  For instance /bin/sh won't be able to run background jobs,
> /bin/csh will close stdin of any background jobs (which might cause
> wierd things to happen), users of daemon(3) won't properly disconnect
> from the tty which started them, and there are a number of references to
> /dev/null in the /etc and /etc/rc.d scripts.
>
> In the case of i386, the size of the text+data size of null.ko is a
> little over 2K.  From a quick look at the source, it looks like at least
> half of this is the module support code.
>
> BTW, I think daemon(3) and /bin/csh should check the return value when
> they attempt to open(_PATH_DEVNULL, ...).

I'd be very surprised if you could do anything useful with a system 
w/o /dev/null.  /dev/zero is getting to be like that too.

Folks promoting this for embedded purposes have not tried to squeeze a running 
system into a few meg (i.e. this change is meaningless in terms of  what 
needs to be done).

	Sam